If the operands of a select instruction are identical, then
this select can be replaced by its operand.
If the condition of a select is a constant, the this select
can be replaced by one of its condition, depending on the
truth value of the condition.
This simplification is already done but:
* when src1 == src2, the condition's value is tested although
it may not be a constant. It's kinda OK because in all case
one of the operand will be selected and both are identical
but it's a bit weird and unclean.
* since the instruction will be replaced, the usage of its
condition and operands must be removed. This is done here but
the kill_instruction() inside replace_with_pseudo() take
already care of this.
So, separate the two cases and simply use replace_with_pseudo()
for both without bothering killing the operands.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
simplify.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/simplify.c b/simplify.c
index 20ea5f1be71a..20ab9b3b3ecf 100644
--- a/simplify.c
+++ b/simplify.c
@@ -1753,14 +1753,12 @@ static int simplify_select(struct instruction *insn)
cond = insn->src1;
src1 = insn->src2;
src2 = insn->src3;
- if (constant(cond) || src1 == src2) {
- pseudo_t *kill, take;
- kill_use(&insn->src1);
- take = cond->value ? src1 : src2;
- kill = cond->value ? &insn->src3 : &insn->src2;
- kill_use(kill);
- return replace_with_pseudo(insn, take);
- }
+
+ if (constant(cond))
+ return replace_with_pseudo(insn, cond->value ? src1 : src2);
+ if (src1 == src2)
+ return replace_with_pseudo(insn, src1);
+
if (constant(src1) && constant(src2)) {
long long val1 = src1->value;
long long val2 = src2->value;
--
2.29.2
